JPH02132441A - Photomask - Google Patents

Abstract

PURPOSE:To eliminate the pattern abnormality based on the nonuniform spacing between a photomask and a substrate with a photosensitive resin by providing >=3 layers of light transmittable layers respectively having prescribed refractive indices between a light transparent substrate and light shieldable patterns. CONSTITUTION:The 1st light transmittable layer 2 consisting of a low-refractive index material, the 2nd light transmittable layer 3 consisting of a high-refractive index material and the 3rd light transmittable layer 4 consisting of the low- refractive index material are formed on the light transparent substrate 1 consisting of a glass plate, etc. The light shieldable patterns 5b consisting of a Cr film, etc., are formed on the layer 4. Molybdenum oxysilicide, etc., are usable for the layer 2, molybdenum nitrosilicide, etc., for the layer 3, and silicon oxide, etc., for the layer 4. These layers are formed by a sputtering treatment, etc. The resist patterns faithful to the patterns 5b are obtd. even if there is the nonequal spacing between the mask and the substrate if such mask is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photomask used when forming various patterns on various substrates by photolithography.

[Prior Art] Conventionally, as a photomask, a light-shielding pattern mainly composed of Cr, Ta, MoSi2, etc. is provided on a light-transmitting substrate such as a glass substrate, and if necessary, a light-shielding pattern is formed on the light-shielding pattern. A device provided with an antireflection film made of an oxide such as chromium oxide is known.

This photomask is used, for example, to form various patterns on various substrates by photolithography using a contact exposure method.

When forming a pattern on a substrate with a photosensitive resin layer by photolithography using this contact exposure method,
The photomask and the substrate with a photosensitive resin layer are brought into close contact by evacuating the space between them, and ultraviolet rays are incident from the photomask side to selectively expose the photosensitive resin layer to improve the light-shielding properties of the photomask. First, a latent image corresponding to the pattern is formed.

Next, by developing the photosensitive resin layer, a desired photosensitive resin pattern is formed on the substrate.

[Problems to be Solved by the Invention] However, when a conventional photomask is used to form a pattern on a substrate by photolithography using a contact exposure method, the following problems occur. In other words, during close exposure, if the adhesion between the photomask and the substrate with a photosensitive resin layer is poor, a gap will be created between them. Interference fringes are generated due to light interference depending on the distance between the two. Corresponding to these interference fringes, the line width of the photosensitive resin pattern obtained after exposure and development changes periodically, and in severe cases, photosensitive resin remains in areas where a photosensitive resin pattern should not be formed. This phenomenon occurs. This non-uniform gap occurs when the photomask or the substrate with the photosensitive resin layer has poor flatness. The above-mentioned non-uniform gap also occurs when air is left between the photomask and the photosensitive resin layer-coated substrate due to insufficient evacuation during contact exposure.

Furthermore, if foreign matter such as dust or resin fragments adheres to the photomask or the substrate with the photosensitive resin layer, the foreign matter will be interposed between the photomask and the substrate with the photosensitive resin layer, resulting in the above-mentioned problems. Uneven gaps occur. In particular, as the close exposure is repeated, the amount of foreign matter that adheres to the photomask gradually increases, and the number of times the photomask can be continuously repeatedly exposed to close exposure is significantly reduced.

Therefore, when using a conventional photomask to form a pattern by photolithography using a contact exposure method, in order to eliminate the above-mentioned non-uniform gaps as much as possible, the planarity of the photomask is increased and the pattern is Measures can be taken such as increasing the flatness of the substrate with the photosensitive resin layer that is formed, ■ lengthening the evacuation time sufficiently, and ■ increasing the cleanliness of the photomask and the cleanliness of the substrate with the photosensitive resin layer. However, even if these measures were taken, it was difficult to always prevent pattern abnormalities based on interference drafts. Moreover, by taking the above-mentioned measures, a pattern without abnormalities may be obtained, but in this case as well, a decrease in productivity and an increase in production costs cannot be avoided.

The present invention has been made in order to eliminate such problems, and its purpose is to provide a photomask and a photosensitive resin layer when forming a pattern on a substrate using photolithography based on a contact exposure method. Even if there is an uneven gap between the mask and the substrate, the pattern abnormalities mentioned above are suppressed, making it possible to form a highly accurate pattern on the substrate that faithfully corresponds to the light-shielding pattern of the photomask. The goal is to provide photomasks that are suitable for

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the present invention provides a photomask having a light-transmitting substrate and a light-blocking pattern, comprising: A light-transmitting multilayer film is provided at least in the region corresponding to the gap between the light-shielding patterns on the top, and the light-transmitting multilayer film includes first and second layers sequentially provided on the light-transmitting substrate. and a third light transmitting layer, the first light transmitting layer is made of a low refractive index material, and the second light transmitting layer is made of a high refractive index material. The photomask is characterized in that the third light transmitting layer is formed of a low refractive index substance.

"Example] Embodiments of the present invention will be described below with reference to the drawings.

Example 1 (see Figure 1) A glass substrate 1 (glass type: aminoborosilicate glass (for example, LE-30 made by HOYAn) with both main surfaces precision polished)
, refractive index 1.52, length 152 mm x width 152 mm x thickness 2.3 mm) was sputtered under the conditions shown in Table 1 to sequentially deposit a first layer of molybdenum silicide oxide on the glass substrate 1. Light transmitting layer 2 (refractive index 1.63>
, a second light-transmitting layer 3 made of molybdenum nitride silicide (
After forming the third light transmitting layer 4 (having a refractive index of 1.47) made of silicon oxide and having a refractive index of 2.8+i0.35>, the layers shown in Table 1 are applied on the third light transmitting layer 4. By performing sputtering under the following conditions, a light-shielding film 5 made of a Cr film was formed to obtain a photomask blank (see figure (a)).
.

Next, a positive electron beam resist PBS is applied on the light shielding film 5.
-C (trade name manufactured by Chisso ■) was applied using a spin coating method to a thickness of 1500 nm to form a resist film, and then exposed to an electron beam to form a desired line and space pattern as described below. A corresponding linear latent image is formed on the resist film, and then a predetermined developer (methyl isoamyl ketone and isopropyl alcohol are mixed in a ratio of 3/1)
A predetermined resist pattern is obtained by performing a development process using the mixed solution (mixed solution) for 60 seconds.

Next, using a mixed aqueous solution of ceric ammonium nitrate and perchloric acid, the light-shielding film 5 in the area where there is no resist pattern is selectively etched to obtain the light-shielding pattern 5p, and then ultrasonically cleaned with methylene chloride. The resist pattern is peeled off by the method, and the first,
To obtain a photomask according to this embodiment, which has the second and third light-transmitting layers 2, 3, and 4, and further has a light-shielding pattern 5p thereon, see FIG. 4(b). In addition, the light-shielding pattern 5p shows a line, and the light-shielding pattern 51), 5p
The spaces indicate spaces. And the line width is 0.8μm
The width of the space is 1.6 μm.

Example 2 By performing sputtering under the conditions shown in Table 2, the first
A photomask of this example was obtained in the same manner as in Example 1 except that the second and third light-transmitting layers were formed.

Example 3 By performing sputtering under the conditions shown in Table 3, the first
A photomask of this example was obtained in the same manner as in Example 1 except that the second and third light-transmitting layers were formed.

○Yu Example 4 On the same glass substrate as used in Example 1, W was used as a target, Ar 50 SCCm was used as a reaction gas,
1 omtorr as pressure, 1 as sputtering power.
After forming a light-shielding film made of W film by sputtering using 5KW, a resist pattern was formed on this light-shielding film in the same manner as in Example 1, and then C was used as a gas.
F4 4 0 sccm + 02 1 osccm, 0 as pressure. 1torr, IOOW as Rf power
The light-shielding film was selectively etched by plasma etching, and the resist pattern was peeled off in sulfuric acid heated to 90° C. to form a light-shielding pattern made of a W film on the glass substrate.

Next, the first, second and third light transmitting layers were formed under the same conditions as in Example 1 to form a light shielding pattern 5p on the glass substrate 1 as shown in FIG. On the light-shielding pattern 5P and on the light-shielding pattern 5P. A photomask of this example was obtained, which had a first light-transmitting layer 2, a second light-transmitting layer 3, and a third light-transmitting layer 4 in this order on a glass substrate 1 between SPs.

Example 5 A light-shielding film made of a Cr film was formed on the same glass substrate as used in Example 1 under the same conditions as the light-shielding film shown in Table 1. In the same manner as in Example 1, a resist pattern was formed, a light-shielding film was etched, and the resist pattern was peeled off to form a light-shielding pattern made of a Cr film on a glass substrate.

Next, as in Example 4, a first light-transmitting layer made of molybdenum silicide oxide was formed by sputtering the glass substrate on the light-shielding pattern and between the light-shielding patterns under the conditions shown in Table 4. A second light-transmitting layer made of silicon nitride and a third light-transmitting layer made of magnesium fluoride were sequentially formed to obtain a photomask of this example.

Comparative Example 1 This comparison has only a light-shielding pattern on a glass substrate by immediately providing a light-shielding pattern made of a Cr film without providing the first, second, and third light-transmitting layers on the glass substrate. An example photomask was obtained.

Next, using the photomasks obtained in Examples 1 to 5 and Comparative Example 1, a linear photosensitive resin pattern corresponding to line and space was formed on a glass substrate by photolithography using a contact exposure method. Ta. The details are as follows. That is, the glass substrate on which the photosensitive resin pattern is to be formed is 152 mm long.
x Using a glass substrate of 152 mm in width x 2.3 mm in thickness,
A positive type photoresist A21350 (manufactured by Hoechst) was applied to this by a spin coating method to a thickness of 1,000 yen, and this was brought into close contact with the photomask.
Contact exposure processing was performed under the conditions of evacuation time of 10 seconds and exposure time of 2.5 seconds.

As a result, interference fringes were visually observed during exposure also when the photomasks of Examples 1 to 5 were used and when the photomask of Comparative Example 1 was used. In both the photomask of the example and the photomask of the comparative example, the fact that interference patterns were visually observed means that an uneven gap exists between the photomask and the resist film-coated glass substrate.

Moreover, when the photomask of Comparative Example 1 is used, interference fringes are generated even in the resist photosensitive region (approximately 350 to 450 nm), so the line width of the resist pattern after development is Pattern line width 0.8μ
There was a periodic change in the part that was about 0.4 μm thicker than m and the part that was almost the same, and an abnormal line width was observed. On the other hand, when the photomasks of Examples 1 to 5 are used, the line width of the resist pattern after the development process is smaller than that of the photomask pattern because no interference pattern occurs in the photosensitive area of the resist. A resist pattern that faithfully corresponds to the photomask pattern was formed on the glass substrate, which was almost the same as the line width (the line width of the photomask pattern was 0.8μm, whereas the line width of the resist pattern was 0.85μm). It had been.

Next, for the photomask of Example 1 and the photomask of Comparative Example 1, reflectance curve diagrams are shown when the distance from the resist film-covered substrate is changed (however, the exposure wavelength was set to 410nllll, which is in the resist photosensitive area). Shown in Figure 3. Note that the above reflectance excludes the reflectance on the glass substrate surface where the photomask pattern is not provided and the glass substrate surface on which the resist film of the resist film-coated substrate is not attached.
It shows the total reflectance at the surface of the glass substrate on which the photomask pattern is provided, the surface of the resist film, the interface between the resist film and the glass substrate, etc. In this figure, ('
a) is the reflectance curve of the photomask of Example 1, (b)
1 and 2 show reflectance curves of the photomask of Comparative Example 1, respectively.

As is clear from curve (a), in the case of the photomask of Example 1 in which three light-transmitting layers were provided on a light-transmitting substrate, the reflectance remained unchanged even if the distance from the resist film-covered substrate changed. 0-5
It only changes with an amplitude of %. Therefore, in the contact exposure method using the photomask of Example 1, the reflectance does not change significantly even if the distance to the resist film changes depending on the location, so the occurrence of interference marks can be suppressed, and the It is clear that abnormalities are less likely to occur in the resist pattern formed.

On the other hand, as is clear from curve (b), in the case of the photomask of Comparative Example 1 without a light-transmitting layer, the reflectance changes with an amplitude of 0 to 16% as the distance from the resist film changes. Changes greatly. Therefore, in the contact exposure method using the photomask of Comparative Example 1, it is clear that when the distance from the resist film changes depending on the location, the reflectance also changes greatly, and this is the cause of the occurrence of interference marks and, ultimately, the occurrence of resist pattern abnormalities. It is.

Next, for the photomask of Example 1 and the photomask of Comparative Example 1, curve diagrams showing the wavelength dependence of reflectance, that is, reflectance curve diagrams when changing the wavelength, are shown in Figures 4, 5, and 5. 6 (however, the distance between the photomask and the substrate with the resist film was constant at 5,000 people in the case of FIG. 4, 4,000 people in the case of FIG. 5, and 3,000 people in the case of FIG. 6).

In Figures 4 to 6, curve (a) is for the photomask of Example 1, and curve (b) is for the photomask of Comparative Example 1, from 350 to 450 nm (corresponding to the resist photosensitive area).
In each figure, curve (a) has a significantly smaller amplitude of reflectance than curve (b) (for example, in Figure 4, curve (a>
The amplitude of the reflectance in curve (
The amplitude of the reflectance in b) is approximately 16%. Therefore, in the case of the photomask of Example 1, which wavelength of light (360 nm, 360 nm,
405 nm, 436 nm, that is, light in the wavelength range used for exposure, pattern abnormalities are less likely to occur due to the small reflectance value, whereas in the case of the photomask of Comparative Example 1, the reflectance It is clear that pattern abnormalities are likely to occur because of the large wavelength range.

Although the present invention has been described above with reference to Examples, the present invention includes the following modifications and applications.

(i) Although a glass substrate was used as the light-transmitting substrate in the embodiment, other light-transmitting substrates such as a plastic substrate may be used.

(ii) In the example, Cr was used as the light-shielding pattern.
Although a pattern of a film or a W film was used, a light-shielding pattern M o S mainly composed of Ta, MoSi2, etc.
A light-shielding pattern whose main component is i2 or the like may be used.

(iii) In the examples, a light-transmitting multilayer film is applied over the entire surface of a light-transmitting substrate (see FIG. 1(b)) or on the light-transmitting substrate on and between light-shielding patterns (see FIG. 2). However, it is sufficient to provide the light-transmissive multilayer film in the region corresponding to the gap between the light-shielding patterns on the light-transmissive substrate.

(iv) The thickness of the first light-transmitting layer constituting the light-transmitting multilayer film was 500 in the example, but the thickness was 400 to 400.
It is preferable to select the number appropriately within the range of 700 people.

In the embodiment, molybdenum silicide oxide and tungsten silicide oxide were used as the material for the first light-transmitting layer, but titanium silicide oxide and tantalum silicide oxide may also be used. It is also possible to use mixtures of these oxidized silicides.

The first light-transmitting layer is a low refractive index layer, and its refractive index is
The refractive index is preferably between the refractive index of the light-transmitting substrate and the second light-transmitting layer, and is usually 1.55 to 1.8.

(V) The thickness of the second light-transmissive layer constituting the light-transparent multilayer film was 750 and 1000 in the examples, but it is preferably selected as appropriate in the range of 700 to 1200. .

In the examples, molybdenum nitride silicide and silicon nitride were used as the material for the second light-transmitting layer, but nitride silicides such as titanium nitride silicide, tantalum nitride silicide, tungsten nitride silicide, zirconium oxide, and titanium oxide It is also possible to use oxides such as. It is also possible to use mixtures of these substances.

The second light-transmitting layer is a high refractive index layer, and its refractive index is
The refractive index should be higher than the refractive index of the first light-transmitting layer and the third light-transmitting layer, and is usually preferably from 1.8 to 3.

(vi) The thickness of the third light-transmitting layer constituting the light-transmitting multilayer film was 550 in the example, but it was 400 to 400.
It is preferable to appropriately select within the range of sooX.

The third optically transparent layer is a low refractive index layer, the refractive index of which should be lower than the refractive index of the second optically transparent layer,
Usually, it is preferably 1.3 to 1.5. This third
It is preferable that the light-transmitting layer has a refractive index lower than that of the light-shielding substrate.

(Vii) In the example, a dielectric multilayer film was formed using three light-transmitting layers, but the number is not limited to three layers, and a light-transmitting multilayer film can be formed using four or more light-transmitting layers. It may be formed.

(Viii) Although the contact exposure method has been described in the embodiment, it goes without saying that no problem will arise if it is applied to other exposure methods, such as reduction projection exposure method.

(ix) In the examples, a glass substrate with a resist film was used as the substrate to be transferred, but photomask blanks, substrates for solar cells, substrates for EL elements, and color filters in which a transparent conductive film is provided on a glass substrate are also used. It may be a substrate for use as an information recording medium, or a substrate for an information recording medium.

[Effects of the Invention] As described above, according to the present invention, when forming a pattern on a substrate, uneven gaps exist between the photomask and the substrate, pattern abnormalities are suppressed, and light shielding of the photomask is achieved. A photomask that can form a highly accurate pattern on a substrate that faithfully corresponds to a physical pattern has been provided.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams showing the photomask of the present invention, and FIGS. 3, 4, 5, and 6 are schematic diagrams showing the photomask of the present invention.
3 is a reflectance curve diagram for a photomask of Example 1 and a photomask of Comparative Example 1. FIG. DESCRIPTION OF SYMBOLS 1...Glass substrate, 2...1st light transmitting layer, 3...
...Second light transmitting layer, 4...Third light transmitting layer, 5
... Light-shielding film, 5 ... Light-shielding pattern p

Claims (1)

[Claims] 1. In a photomask having a light-transmitting substrate and a light-shielding pattern, a light-transmitting multilayer film is provided at least in a region of the light-transmitting substrate corresponding to the gap between the light-shielding patterns. The light-transmitting multilayer film is composed of at least three light-transmitting layers including first, second, and third light-transmitting layers sequentially provided on a light-transmitting substrate, The first light transmitting layer is made of a low refractive index material, and the second light transmitting layer is made of a high refractive index material,
Furthermore, the photomask is characterized in that each of the third light-transmitting layers is formed of a low refractive index material.